Modified, precipitated alumino silicate pigments and an improved method for preparing same

ABSTRACT

Novel alkali aluminum silicate particulates modified with and containing a chemically bound alkaline earth metal, and a method for producing same is disclosed. The alumino silicate pigments contain an alkaline earth metal, preferably calcium, magnesium or barium in addition to an alkali metal, such as sodium. In chemical composition, the pigments contain oxides of the alkaline earth metal, the alkali metal, aluminum and silicon and are distinguishable from co-precipitates. The pigments are prepared by introducing dilute solutions of an alkali silicate and an aluminum salt of a mineral acid into an agitated aqueous receiving medium containing an alkaline earth salt or hydroxide. The pH of the fuild reaction medium may be controlled to form finely divided precipitated particulates having improved properties and which may be used as pigments in paper, paint, rubber, inks, plastics and the like.

United States Patent Fitton v MODIFIED, PRECIPITATED ALUMINO SILICATE PIGMENTS AND AN IMPROVED METHOD FOR PREPARING SAME [75] Inventor: Robert C. Fitton, Bel Air, Md.

[73] Assignee: J. M. Huber Corporation, Locust,

22 Filed: Nov. 5, 1971 211 Appl.No.:198,022

[52] US. Cl. 106/306, 106/288 B [51] lint. Cl. C09c 1/02 [58] Fleld of Search 106/306, 288 B, 308, 309

[56] References Cited I t h d d h icuaes avmg improve proper 1es an w 1c may UNITED STATES PATENTS be used as pigments in paper, paint, rubber, inks, plas- 2,739,073 3/1956 Bertorelli 106/288 B tics and the like 2,848,346 8/1958 Bertorelli 106/288 B Primary Examiner-Delbert E. Gantz Assistant Examiner-James W. Hellwege Attor riey, Agent, or Firm-Harold H, Flanders [111 dflddfidd [451 Mall. 19, 19%

[5 7] ABSTRACT Novel alkali aluminum silicate particulates modified with and containing a chemically bound alkaline earth metal, and a method for producing same is disclosed. The alumino silicate pigments contain an alkaline earth metal, preferably calcium, magnesium or barium in addition to an alkali metal, such as sodium. In chemical composition, the pigments contain oxides of the alkaline earth metal, the alkali metal, aluminum and silicon and are distinguishable from coprecipitates. The pigments are prepared by introducing dilute solutions of an alkali silicate and an aluminum salt of a mineral acid into an agitated aqueous receiving medium containing an alkaline earth salt or hydroxide. The pH of the fuild reaction medium may be controlled to form finely divided precipitated par- 9 Claims, 5 Drawing Figures PATENTED MAR 1 9 I874 SHEET 2 OF 5 FIG. 2

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to finely divided precipitated silicate pigments and, more particularly, to an unique method for preparing modified sodium alumino silicate pigments which are chemically analagous to zeolites but which have greatly improved properties and characteristics.

2. Description of the Prior Art As is well known in the art, natural alkali metal zeolites such as natrolite and analcine are known to possess water softening properties but have limited usefulness as pigments. In recent years a number of artificial or synthetic zeolites containing sodium, aluminum and silicon oxides, in various proportions, have been proposed and synthesized. Examples of synthetic zeolites are disclosed in US Pat. Nos. 2,882,243; 2,962,355; 2,996,358; 2,010,789; 3,011,869; and 3,012,853. To a large extent, known synthetic zeolites lack the essential characteristics of pigments and have found limited use in this field.

In this regard, however, there has been developed a novel precipitated sodium alumino silicate that has particular use as pigments in paper coatings, as fillers in rubber compounds, in inks, paints, plastics and the like. Such pigments are commercially available and are manufactured and sold under the trademark Zeolex by .I. M. Huber Corporation. While Zeolex pigments contain the essential oxide components of natural and synthetic products, these pigments are precipitated products of alumina and silica and contain chemically bound sodium and as such are readily distinguishable from gels and other synthetically produced materials. In general, these pigments are precipitated amorphous materials and are composed of particles having ultimate'sizes of only a few hundredths of a micron in diameter which tend to cling together in clusters of up to about 1 micron in diameter. In chemical composition, they typically contain Na O and A1 0,, in a molar ratio near to l, as in the range of about 0.8 to 1.2 mols of Na O per mol of A1 together with silica which can be present in any of various selected concentrations ranging from as little as about 2.5 mol to as much as about 16 mols of SiO per mol of A1 0 As will be discussed in more detail hereinafter, these pigments are advantageously prepared (see e.g., US. Pat. No. 2,739,073) by comingling dilute solutions of an alkali silicate and an aluminum salt, such as aluminum sulfate. In a preferred embodiment, an amount of water not greater than about one half-of the volume of the solutions to be added is placed in a suitable reaction vessel provided with a strong agitator. The reactants, i.e., the dilute solutions of the alkali silicate and an aluminum salt, are then introduced in streams entering the water at widely spaced points. In US. Pat. No. 2,848,346 such pigments are prepared by comingling a dilute solution of an alkali silicate and a dilute solution of a dispersion containing finely divided silica and aluminum sulfate. The latter is prepared by treating kaolin clay with a strong mineral acid, such as sulfuric acid.

SUMMARY OF THE INVENTION In summary, the present invention is directed to the production of novel modified sodium alumino silicate pigments. In its broadest aspects, the invention is characterized and embodies the concept of producing a pigment having significantly improved properties by introducing an alkali metal silicate and an aluminum salt into an agitated receiving medium which contains an 0 alkaline earth metal salt, such as magnesium sulfate. It

has been discovered that products produced in this contain chemically bound sodium (i.e., the alkali metal) as well as the chemically bound alkaline earth metal. As such the products are readily distinguishable from so-called co-precipitates which contain mere mixtures of e.g., an alkali metal alumino silicate and an alkaline earth metal alumino silicate.

From the above and as will be evident from the following detailed description, the present invention provides a truly unique and simplified process for preparing novel alkaline earth metal modified synthetic Zeolitic-type products having greatly improved properties.

It is accordingly a general object of the present invention to provide a novel zeolitic-type product and an improved method for preparing same.

Another and more particular object is to provide novel modified alumino silicate pigments that are especially useful in paper coatings.

Another and more particular object is to provide a highly efficient and improved method for preparing finely divided precipitated alkaline earth-alkali metal alumino silicate pigments.

Yet another object is to provide novel modified sodium alumino silicate particulates which have particular utility for use in paper, but which may be also advantageously employed as reinforcing pigments or fillers in rubber, in inks, paints, plastics and the like.

Still another object is to provide an improved method for preparing modified silicate pigments, said method being characterized by its high flexibility in producing a product of a given or predetermined property or characteristic.

Yet still another object is to provide an economical and practical method for producing modified sodium alumino silicate pigments having greatly improved properties, said method not being subject to the disadvantages and complexities involved in prior known techniques.

BRIEF DESCRIPTION OF THE DRAWINGS The manner in which the foregoing and other objects are achieved in accordance with the present invention will be better understood in view of the following detailed description and the accompanying drawings, which form a part of the specification, and wherein:

FIGS. 1 and 2 are prints of microphotographs illustrating novel magnesium sodium alumino silicate pigments produced in accordance with the present invention, and;

FIGS. 3 and 4 are prints of microphotographs illustrating finely divided precipitated sodium alumino silicate pigments of the type produced in accordance with the prior known techniques.

FIG. 5 is a graph showing reaction pH ranges vs. reaction time in minutes for the production of precipitated alumino silicate pigments in accordance with method embodiments of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT(S) In accordance with the present invention, it has been discovered that novel alkaline earth metal modified alkali metal alumino silicate pigments can be prepared by introducing dilute solutions of an alkali metal silicate and a water soluble salt of aluminum and a strong acid (such as aluminum sulfate) into an aqueous reaction media containing dispersed therein an alkaline earth metal salt or hydroxide. The invention is based, in part, on the discovery that if the dilute solutions of the alkali metal silicate and the aluminum sulfate are added to a reaction mass that contains the alkaline earth metal salt or hydroxide, the latter serves as a nucleus or nucleating agent which alters the structure of the resulting modified zeolitic type pigment.

The products of the invention are compositions containing essentially the oxides of an alkaline earth metal, an alkali metal, aluminum and silicon, that may be represented by the general formula wherein X is an alkali metal such as sodium or potassium and Y is an alkaline earth metal of Group 2a of the Periodic Table. The alkaline earth metal is preferably magnesium or calcium. The small letters, i.e., a, b,

e, represent the mols of the oxides present in the total composition. As briefly discussed above, the mol ratio of the constituent oxides may vary widely with the molar ratio of Na O to Al O preferably being near to 1, such as about 0.8 to 1.4 mols of Na O per mol of Al The mols of SiO; to A1 0 can be as low as about 2.5 mols up to as much as about 24 mols of SiOZ per mol of A1 0 'The mantras of thc al k aline earth oxide (YO) to M 0 can be varied from about 0.1 to 3, preferably from about 1.0 to 1.5. From the above, however, it should be readily understood that a change in the molar ratio of any given two oxides will vary the ratio of one such oxide to another, i.e., a third oxide in the composition. To this end it is more simply stated that the alkaline earth metal salt is added to the reaction medium in an amount such that the alkaline earth metal oxide comprises from about 0.1 to 30 percent of the dry weight of the pigment, based on the particular alkaline earth metal salt used. For example if a magnesium salt is employed, the range of the resulting MgO would be about 0.1 to 8.0 percent. With this parameter the other constituents or reactants, e.g., the alkali metal silicate, can be added in an amount to give the desired molar ratio of Na O to A1 0 etc..

The precipitated products have been found to have particle sizes substantially the same as the above discussed Zeolex pigments, i.e., all less than one micron in diameter and moreover are characterized by increased brightness (when used in paper) and other qualities as will be discussed in more detail hereinafter.

ln practicing the method of the present invention, the solutions of the aluminum salt and the alkali metal sili cate are maintained at very low concentrations and under strong agitation during the process of comingling and reacting them together in the body of the reaction mass containing the nuclei, i.e., the alkaline earth salt or hydroxide.

In accordance with a first method embodiment of the present invention, the dilute solutions of the reactants are charged slowly into the diluting aqueous medium containing the alkaline earth metal salt and are preferably introduced at widely spaced locations therein. The reaction mass is continuously and vigorously stirred or agitated throughout the reaction so as to keep the dispersion in a fluid condition. The alkali metal silicate solutions so used should be about 2 molar or lower concentration, and the concentration of the solution of the aluminum salt should also be about 2 molar or lower concentration.

The reaction medium, i.e., the body of water containing the alkaline earth salt, should preferably be about half the combined volumes of the silicate solution and aluminum salt solution. ln this regard, the concentration of the solutions in the reaction mass should average less than about 2.0 molar, depending somewhat upon the particular reactants employed, their purity and other variables. Preferably the reacting concentration is maintained at not more than about 1.0 molar. The dilute solutions of the reactants are introduced into the reacting media at widely spaced points so that a high degree of dilution of each solution is assured. For example, one solution may be added to the vortex created by the agitator blade, while the other solution is added near the wall of the vessel. Alternately, the two solutions may be introduced into the reaction vessel at different levels as e.g., one below the surface with the other being near or above the surface, etc.. Although the reaction mass may thicken somewhat as the precipitation proceeds, at the end of the reaction it is a fluid mass from which the precipitated solid products of the invention may be easily separated.

In general, the addition of the silicate and aluminum salt can be started simultaneously or a portion of the silicate can be added prior to the addition of the aluminum salt. The pH of the reaction should be maintained between about 8 to 12, preferably from between about 8 and 10, until all of the alkali silicate has been added. The addition of the aluminum salt solution may then be continued until the pH is reduced to between about 8 and 10.0. While the precipitation of the product of the invention can be executed by the simultaneous addition of the alkali silicate solution and the aluminum salt solution, it has been found to be particularly advantageous to add a portion of the solution of the alkali metal silicate (such as sodium meta or disilicate) to the receiving medium prior to the introduction of the solution of the aluminum salt. It is not understood how this affects the mechanics of the reaction or precipitating process other than perhaps affecting the nucleating effect of the alkaline earth metal salt. However products produced in accordance with the second method embodiment have further improved properties, particularly with regard to their brightness and their optical properties in paper. In practicing the second method embodiment, the sodium silicate solution is added to the reaction or receiving media until the pH of the aqueous mass is between 8 and 10. Thereafter the solutions of the sodium silicate and the aluminum salt are added simultaneously to the reaction mass until such time as the total amount of the aluminum salt solution has been added. After the aluminum salt solution has been added, the addition of the silicate solution is continued until the pH of the reaction mass is between about 8.0 to 10.0.

Upon completion of the reaction procedure, the precipitated pigment is usually separated from the reaction liquid by filtration, but other means of separation, such as centrifuging, can be used. In general it is preferable to wash the separated pigment with water to remove water soluble salts and the like. The resulting filter cake is then dried in any suitable manner. The drying is preferably performed at elevated temperatures with the temperature of the drying step being used to control the percent of the water of the finished pigment. For example, when dried at about 105C, the pigments usually contain from about 7 to 12 percent water.

It should also be understood that the amount of water remaining in the precipitated pigment depends upon the time, temperature and other conditions of drying. It is not possible to express conditions which will be required for drying a particular pigment with any degree of exactness. This will vary to a large extent, depending e.g., upon the degree of air circulating through the pigment, the type of drying apparatus, etc. As recognized by those skilled in the art, there is a substantial difference in the manner in which free water and bound water are held in pigment compositions. Bound water appears to be chemically combined with the silicate pigment. For this reason bound water does not readily come off unless dried at temperatures on the order of about 300C. On the other hand, free water comes off readily upon drying at relatively moderate temperatures i.e., up to about 105C.

As discussed above the starting materials or reactants employed in the present invention include alkali metal silicate, the alkaline earth salts or hydroxides and aluminum salts. As used herein, the term alkali metal silicates include all the common forms of alkali metal silicates as, for example, metasilicates, disilicates and water glass. Water soluble potassium silicates and sodium silicates are particularly advantageous. Because of their relatively low cost, sodium silicates are preferred. If employed, sodium silicates are effective in any composition in which the ratio of the SiO;; to Na O is from about 1 to 3.321.

The aluminum salts useful in the method of the invention are the water soluble acid salts of aluminum such as aluminum sulfate, aluminum chloride, aluminum nitrate and ammonium alum (aluminum ammonium sulfate). Additionally, the aluminum sulfate solution that is added to the reaction mass may comprise an aqueous slurry of a finely divided precipitated silicon suspended in a dilute aqueous solution of the salt of aluminum and a mineral acid. In this regard, the aqueous reactant solution containing the pre-precipitated silica in suspension with the solution of the aluminum salt can be obtained by employing finely divided kaolin as a basic raw material and decomposing the kaolin in an aqueous suspension with sulfuric acid. The term kaolin is used herein to designate kaolin or like clays composed predominately of the mineral kaolinite. The decomposition of the kaolin may be carried out in an open vessel if the kaolin has been previously roasted or if unroasted kaolin is used it should be reacted with the acid in a closed vessel at pressures on the order of about 150 to 160 psi as disclosed in U.S. Pat. No. 2,848,346. The product of this decomposition process is essentially a dilute solution of aluminum sulfate containing very finely divided free silica in suspension.

The alkaline earth salts or hydroxides employed in the present invention include the salts or hydroxides of metals from Group 2a of the Periodic Table such as magnesium, calcium and barium. Preferred salts are the water-soluble salts such as the sulfates, carbonates, nitrates and chlorides. However others can be employed. It has been found that the use of calcium carbonate and magnesium sulfate are particularly advantageous and thus are preferred.

As indicated above, the unique pigments of the present invention may be advantageously employed or used in paper coatings, as reinforcing pigments in rubber compositions, in paints, inks, plastics and the like. Such pigments may, for example, be employed as reinforcing pigments in various rubber compositions including natural rubber and synthetic rubber compositions including butadiene 1,3-styrene copolymers, butadieneacrylonitrile copolymers, butadiene-isobutylene copolymers and like synthetic elastomers. If employed as rubber pigments of the type described, the alkali silicates should contain from about 1 to about 3.3 molar equivalents of SiO per molar equivalent of Na O.

While the pigments produced in accordance with the invention may be employed in many applications, it has been unexpectedly discovered that the products obtained herein are particularly and excellently suited for use in paper. In this regard, pigments produced for paper fillers as described herein should employ alkali silicates having SiO in a molar ratio of from about 1.5 to about 3.3 to the content of the alkali oxide (Na O).

Before turning to specific examples of the invention it should be noted that while the pH of the reacting medium is maintained in the range of about 8l2, a unique feature of the invention lies in the ability to produce a given product consistently even through the pH isvaried during the reaction period or is held constant therethrough. Also by changing the pH of the reacting mass, pigments of different properties and characteristics can be produced.

The following Examples will serve to further illustrate the present invention but it is expressly understood that they are not intended to limit it thereto. The Tables which follow the Examples set forth specific properties and characteristics of the products of the Examples not otherwise included therein.

EXAMPLE 1 A dilute alkali silicate solution was prepared by dissolving 4,740 lbs. of sodium silicate (Na O 2.5 SiO in 2,370 gallons of water. A separate dilute solution of aluminum sulfate was prepared by dissolving 2,500 lbs. Al (SO,,) 141-1 0 in 1,000 gallons of water. A 7,500 gal. reaction vessel provided with a propeller type agitator blade was charged with 1,540 gallons of water to which was added 1,282 lbs. of MgSO 7 H 0, and the agitator was started. The sodium silicate solution was charged to the reaction vessel at a rate of 46.5 GIPM as a thin stream directly into the vortex formed by the rotating agitator blade. The addition of the sodium silicate solution was continued for a period of 16 minutes at the end of which time the pH of the reaction mass was 9.9. Thereafter, and with the silicate solution still being introduced, the aluminum sulfate solution was introduced at a rate of 25. l GPM for an additional period of 35 minutes. The pH, during the simultaneous addition of the silicate solution and the aluminum salt, was reduced to about 9.5. At the end of the 511 minute reaction period all the silicate solution had been added.

Thereafter the addition of the aluminum sulfate solution was continued until the final pH of the reaction mass was 8.8. This required an additional 5.0 minutes. The temperature of the solutions of the reactants introduced into the reaction vessel as well as the receiving medium was maintained at about 65C throughout the reaction. After the pH of the reaction mass was reduced to 8.8 and all of the sulfate salt had been added, agitation of the reaction mass was continued for an additional 15 minutes. The precipitate was then separated by filtration and thoroughly washed with water at ambient temperatures. The resulting filter cake was dried at 110C. The cake was pulverized in a hammer mill. The material so produced was a finely divided white particulate made up of particles less than 0.5 microns in diameter and about 97 percent of which were less than 0.05 microns in diameter. The product of this example is shown in the microphotograph of FIG. 1. The specific gravity of the product was 2.2. The pour density was 9.5 lbs. per cubic foot and the product had a BET surface area of 97m /g. From a chemical analysis of the product the following formula was calculated: 1.3 Na O 1.0 A1 1.2 MgO- 14.3 SiO 4.3 H 0 EXAMPLE 2 The procedure of Example 1 was repeated except that the sodium silicate employed contained 1.4, 1.83, 2.34, 2.8, and 3.35 mols of SiO per mol of Na O respectively. The products obtained in this Example possessed properties similar to those of product of Example 1.

EXAMPLE 3 The general procedure of Example 1 was repeated except that magnesium chloride, magnesium hydroxide, and magnesium nitrate, were substituted for the magnesium sulfate of Example 1. The products obtained were substantially the same as that in Example 1.

EXAMPLE 4 The general procedure of Example 1 was repeated except that the aluminum sulfate and sodium silicate solutions were added simultaneously at the outset of the reaction or precipitation process. In addition the pH of the reaction mass was maintained constant (80) by adjusting the rate of addition of the two solutions. At the end of the reaction period, which required 51 minutes, the final pH of the slurry was increased to 9.5 by the addition ofa dilute solution of the silicate. This required an additional 3 minutes. The product produced in this Example was substantially the same as the product of Example 1 and is shown in the microphotograph of FIG. 2.

EXAMPLE 5 The general procedure of Example 1 was repeated except that aluminum chloride, aluminum nitrate and ammonium alum were substituted for the aluminum sulfate employed in Example 1. The products produced were substantially the same as that of Example 1.

EXAMPLE 6 was added 1,081 lbs. of calcium sulfate and 1,053 lbs. of calcium carbonate, respectively. After the precipitate was recovered by filtration, washed and dried, the product from test run No. 2 was reslurried and treated with sufficient HCl to reduce the pH of the slurry to about 3.5. Thereafter sufficient NaOH was added to the pigment slurry to increase the slurry pH to 8.8. The products obtained both prior to and after the additional treatment with NaOH possessed properties similar to that of the products of Example 1. In a series of further tests the above general procedure was repeated except that the amount of the calcium salt was varied and sodium silicate was substituted for the NaOH. (See Table 3 below).

EXAMPLE 7 The procedure of Example 1 was repeated except that the aluminum sulfate solution consisted of a slurry of finely divided precipitated silica in a solution of aluminum sulfate that was prepared by reacting 3250 lbs. of commercial kaolin with 4,000 lbs. of percent sulfuric acid in 1,000 gallons of water. The slurry was formed by agitating the kaolin with the sulfuric acid in a lead line autoclave at a temperature of C for 10 hours. This reaction mass was cooled, discharged and made up to volume of 3,000 gallons by the addition of water. In examination, the finely divided precipitated silica particles suspended in the aqueous solution of aluminum sulfate showed that almost all the precipitated silica particles were less than 0.2 microns in its greatest dimension. The separate dilute solution of the sodium silicate and the aluminum sulfate solution containing the finely divided precipitate silica was then charged to the reaction vessel in the manner of Example 1. The precipitate was recovered by filtration with water and dried at l 10C. The filter cake was obtained in the form of soft lumps. On passing these lumps through the hammer mill a white powder was obtained, substantially all the particles of which were smaller than 0.5 microns in their greatest diameter.

EXAMPLE 8 The procedure of Example 1 was repeated except that the reaction vessel was charged with 1,500 gallons of water to which was added 1,085 lbs. of barium sulfate. The product produced in this Example was substantially the same as that of Example 1.

EXAMPLE 9 The procedure of Example 1 was repeated except that a mixture of MgSO 7 H 0 and CaCO (641 lbs. each or a total of 1,282 lbs.) was charged to the reaction vessel containing 1,540 gallons of water. The general properties of the product produced in this Example (e.g., particle size, surface area, density, etc.) were similar to those of the product of Example 1. Further properties of the pigment are shown in the Table set forth hereinbelow.

EXAMPLE 10 The general procedure of Example 1 was used to prepare 7 batches under varied reaction pH ranges. FIG. 5 shows the reaction pH ranges under which these batches were precipitated. These Examples clearly establish the flexibility of the method of the invention to produce a given product consistently. Table 4 shows the effect of these variations on the physical properties 3,798,046 9 of the product. Table 5 illustrates the fine paper propexcept that EH6 'a'fii'diifit (51 the Mg S OQ added to the reerties of the products produced in accordance with this ceiving medium was varied (See Table 2 below) such Example. that the final product contained varying amounts of EXAMPLE 1 1 magnesium based on the dry weight of the product.

The general procedure of Example 1 was repeated --'""TABI CHEMICAL-PHYSICAL PROPERTIES OF PIGMENTS MODIFIED WITH MAGNESIUM AND CALCIUM Pigment Valley Oil BET (Elrepho) 325 Abrasion Absorption Density, lbJft Surface Pigment Brightness LOl pH Residue mg loss ed g Pour Pack Area Ex.l MgSO 90.8 7.0 11.3 4.4 6.2 132 10.0 20.9 97 Ex. 2 MgSQ 91.6 8.1 10.9 3.7 2.7 140 8.6 18.3 114 Ex. 2 MgSO 91.6 8.1 11.4 5.1 5.5 156 10.0 21.6 106 Ex. 2 MgSO, 91.0 7.6 11.2 3.6 10.9 10.4 22.4 102 Ex. 2 MgSO, 91.1 7.5 11.3 4.8 7.5 10.0 17.5 122 Ex. 2 MgSO, 91.7 8.0 11.3 0.9 8.0 136 10.8 22.0 105 Ex. 3 MgCl 90.4 9.7 10.6 0.8 4.3 138 10.2 20.1 142 Ex. 3 M (OH 2 90.8 9.2 10.4 2.4 7.8 131 10.2 22.3 142 Ex 3 M NO 91.0 9.6 1 0.l 1.8 6.8 135 12.0 25 .0 5X4 MgSOi -Q. 1 4- 3 3.111 9 .2..29- ..-w. -lfi Ex. 6 CaSO, m 90.8 WT 8.5 T1 3 1.25 6.0 132 10.1 20.8 105 Ex. 6 CaCO 91.0 9.3 10.9 0.81 8.0 170 9.9 22.0 111 Ex. 8 132150 91.2 9.0 11.3 1.01 6.5 10.2 23.2 112 Ex. 9 MgSO & CaCO 91.4 8.9 11.0 1.04 7.5 156 10.4 20.4 130 TABLE 2 FINE PAPER PROPERTIES OF PlGMENTS MODlFlED WITH MAGNESIUM Solids %F %Mg in of Wet l Pigment TAPPI TAPPl Pigment Pigment Cake L Retention Brightness Opacity Unfilled Zeolex 87.0 80.0

23-Contro1 Example 11 None 28.4 3 56 88.0 81.2

Example 11 0.43 26.4 3 49 88.0 81.6

Example 11 0.49 27.5 3 48 87.9 81.6

Example 11 0.43 29.3 3 48 88.0 81.6

Example 11 0.55 26.4 3 57 88.0 81.5

Example 11 0.56 29.7 3 51 88.2 81.6

Example 11 1.5 28.7 3 53 88.9 81.6

Example 11 3.3 24.0 3 48 88.9 81.7

Example 11 2.7 26.0 3 48 89.0 81.2

Example 11 2.7 24.1 3 44 89.0 81.5

Example 11* 1.8 27.3 3 44 89.2 81.0

Example 11 8.0 26.6 3 45 89.2 81.7

Note: in this test. pigment reslurried and treated in accordance with Example 6.

FINE PAPER PROPERTIES OF PIGMENTS MODIFIED WITH CALCIUM AND BARIUM Solids %F Ca in 01 Wet I Pigment TAPPI TAPPI Pigment Pigment Cake L Retention Brightness Opacity Unfilled 88.0 80.3 Zeolex 23 None 28.6 3 55 88.7 82.0 (Control) 6 53 89.0 82.5 9 52 89.2 84.3

Example 6 0.4 24.3 3 52 88.7 82.2 (CaSOJ 6 57 89.1 83.7 9 56 89.4 84.7

Example 6 0.55 23.6 3 47 88.9 82.1 (CaSOJ 6 49 89.1 83.6 9 46 89.4 84.7

Example 6 4.1 25.4 3 47 89.2 82.0 (C350 6 49 89.4 83.4 9 47 89.7 84.6

Example 6 4.3 25.2 3 47 89.2 82.0 caco 6 49 89.4 83.3 9 47 89.7 84.4

Example 6 4.6 28.8 3 47 89.6 82.4 (CaSO,) 6 49 89.9 84.1 9 46 89.9 85.5

Example 6 3.9 29.0 3 47 89.1 82.2 c co 6 47 89.4 83.8 9 46 89.6 85.1

% Ba in Pigment Example 8 4.0 28.7 3 46 V 8 9 .1 8 2.2

(BaSOJ 6 49 89.4 84.0 9 46 89.6 86.3

- TABLE 4 7. .3

PHYSICAL PROPERTIES AND REACTION CONDITIONS OF PIGMENTS MODIFIED WITI-I MAGNESIUM IN ACCORDANCE WITH EXAMPLE 10 Min. Valley %325 BET Sur Oil Pigment Run Excess Prec. pH Final Abrasion screen face area Absorption Brightness No. Silicate Range pH LOI mg-Ioss residue rnlg cc/ 1 g I 16 10.0-10.0 8.8 6.52 4.5 0.24 110 112 93.3 2 16 10.0-9.0 8.8 6.81 5.6 0.16 101 110 93.5 3 16 10.0-9.0 8.8 6.53 6.5 0.12 71 108 93.3 4 2O 10.5-10.5 8.8 6.42 5.6 0.48 124 118 92.7 5 20 10.5-9.5 8.8 6.43 4.2 0.12 108 120 93.3 6 20 l0.5-9.5 8.8 6.55 2.9 0.14 82 110 93.5 7 6 8.0-8.0 9.8 7.06 4.1 0.06 75 137 94.5 8 6 8.0-9.0 9.8 6.38 2.9 0.04 59 127 94.1 9 6 8.0-9.8 9.8 6.56 1.5 0.10 61 136 93.2

FINE PAPER PROPERTIES OF DRIED AND MILLED MAGNESIUM MODIFIED SILICATE PIGMENTS PRODUCED IN ACCORDANCE WITH EXAMPLE 10 Minutes Pigments Run Excess Prec. pH Final Pigments Tappi Tappi No. Silicate Range pH Filler Retention Brightness Opacity Control unfilled 85.6 82.0 1 l6 10.0-10.0 8.8 3 50 87.1 85.0 6 49 87.9 87.0 9 48 88.5 88.3 2 16 10.0-9.0 8.8 3 51 87.1 85.0 6 51 87.9 87.2 9 50 88.5 88.5 3 16 10.0-9.0 8.8 3 51 87.1 85.0 6 52 87.9 87.2 9 52 88.6 88.6 4 20 10.5-10.5 8.8 3 87.1 84.8 6 50 87.9 86.9 9 47 88.5 88.2 5 20 10.5-9.5 8.8 3 50 87.1 84.8 6 50 87.9 86.9 9 48 88.5 88.1 6 20 10.5-9.5 8.8 3 48 87.1 85.0 6 47 88.0 87.1 9 50 88.6 88.5 7 6 8.0-8.0 9.8 3 50 87.3 85.4 6 49 88.3 87.6 9 50 89.1 89.0

FINE PAPER PROPERTIES OF DRIED AND MILLED MAGNESIUM MODIFIED SILICATE PIGMENTS PRODUCED IN ACCORDANCE WITH EXAMPLE Minutes Pigments Run Excess Prec. pH Final Pigments Tappi Tappi No. Silicate Range pH Filler Retention Brightness Opacity What is claimed is:

l. A method for producing finely divided, precipitated alumino-silicate particulates, said method comprising the steps of introducing dilute aqueous solutions of an alkali silicate and a salt of aluminum and a mineral acid into an agitated aqueous receiving medium containing an alkaline earth salt or hydroxide, said introduction of the solutions of said silicate and said salt being such that at least a portion of the solutions of said silicate and salt are added simultaneously; maintaining the resulting reaction mass at a pH in the range of about 8 to 12 during the reaction to thereby produce in said fluid reaction medium very fine white precipitate particulates composed principally of oxides of an alkaline earth metal, an alkali metal, aluminum and silicon, said finely divided precipitated particulates all being less than 1 micron in diameter.

2. The method in accordance with claim 1 wherein said dilute solutions of said alkali silicate and aluminum salt are introduced into said aqueous receiving medium 'atwiaeiyspaed points, and whe r in' siid $16511??? the alkali silicate and aluminum salt are not more than 1 molar concentration and said alkali silicate contains SiO and Na O in a molar ratio of from about 1 to 3.3: l. H 3. "l lie method in accordance with claim 2 wherein the initial volume of said aqueous receiving medium is at least half the combined volume of said solutions of the alkali metal silicate and the aluminum salt and wherein said alkaline earth salt or hydroxide is present in said receiving medium in an amount such that the alkaline earth metal comprises from about 0.1 to 8.0 percent based on the dry weight of the precipitated particulate.

4. The method in accordance with claim 1 wherein the aqueous reaction mass is maintained at a pH in the range of about 8 to 12 while combining said solutions of the alkali silicate and the aluminum salt; said method further comprising reducing the pH of the fluid reaction medium to a pH of between about 8 to 9.5 at the end of the reaction period.

5. The method in accordance with claim 1 wherein the alkaline earth salt is a water soluble salt of calcium, magnesium or barium.

6. The method in accordance with claim 1 wherein said aluminum salt includes a finely divided precipitated silica suspended in an aqueous dilute solution thereof.

7. A method for producing finely divided, precipitated alkaline earth alkali metal alumino-silicates having particular utility for use in paper, said method comprising the steps of introducing a dilute aqueous solution of an alkali silicate selected from the group consisting of sodium and potassium silicates into an agitated aqueous receiving medium containing an alkaline earth salt selected from the group consisting of the water soluble salts of magnesium, calcium and barium or mixtures thereof; continuing the addition of said alkali silicate to said receiving medium until the pH of said receiving medium is at least 8 and for a period of time to effect an initial reaction between said alkali silicate and said alkaline earth salt; introducing a dilute solution of a salt of aluminum and a mineral acid into said receiving medium while continuing the addition of said alkali silicate; said simultaneous addition of the alkali silicate and aluminum salt being controlled such that the pH of the fluid reaction medium is in the range of 8 to 12 to thereby produce in said medium very fine white precipitated particulates composed principally of oxides of said alkaline earth metal, said alkali metal,

aluminum and silicon; adjusting the pH of the fluid reaction medium to between about 8 to 10, and separating, drying and disintegrating said precipitates to obtain a pigment having a particle size of not greater than 1 micron in diameter.

8. The method in accordance with claim 7 wherein said dilute solutions of the alkali silicate and aluminum salt are not more than l molar concentration and said alkali silicate contains SiO and Na O in a molar ratio of from about 1 to 3.321, said method further comprising maintaining the concentration of said alkaline earth salt in said receiving medium such that the alkaline earth metal comprises from about 0.1 to 30.0 percent based on the dry weight of the precipitated particulate.

9 The method in accordance wit h claim 7 wherein said dilute solution of the aluminum salt includes finely divided precipitated silica suspended therein.

UNITED STATES PATENT omits CERTIFICATE OF QQRRECHN Patent No. 3 798 ()46 Dated March 19, I974 Inventor(g) Robert C. Fitton It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Abstract, fifth line from bottom, fuiIcP' shouid be 7-.- fIuid CoIumn I3 and I4, TabIe 5 Continued, the properties for'Run N0. 9

shouId be:

Minutes Pigments Run Excess Prec. pH Fina] Pigments Tappi Tappi M SiIicate Range P FiHer Retention Brightness Opacity Signed, and sealed this 24th day of December 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) USCOMM-DC 60376-1 69 U.S, GOVERNMENT PRINTING OFFICE: I969 0-366-33 

2. The method in accordance with claim 1 wherein said dilute solutions of said alkali silicate and aluminum salt are introduced into said aqueous receiving medium at widely spaced points, and wherein said solutions of the alkali silicate and aluminum salt are not more than 1 molar concentration and said alkali silicate contains SiO2 and Na2O in a molar ratio of from about 1 to 3.3:1.
 3. The method in accordance with claim 2 wherein the initial volume of said aqueous receiving medium is at least half the combined volume of said solutions of the alkali metal silicate and the aluminum salt and wherein said alkaline earth salt or hydroxide is present in said receiving medium in an amount such that the alkaline earth metal comprises from about 0.1 to 8.0 percent based on the dry weight of the precipitated particulate.
 4. The method in accordance with claim 1 wherein the aqueous reaction mass is maintained at a pH in the range of about 8 to 12 while combining said solutions of the alkali silicate and the aluminum salt; said method further comprising reducing the pH of the fluid reaction medium to a pH of between about 8 to 9.5 at the end of the reaction period.
 5. The method in accordance with claim 1 wherein the alkaline earth salt is a water soluble salt of calcium, magnesium or barium.
 6. The method in accordance with claim 1 wherein said aluminum salt includes a finely divided precipitated silica suspended in an aqueous dilute solution thereof.
 7. A method for producing finely divided, precipitated alkaline earth alkali metal alumino-silicates having particular utility for use in paper, said method comprising the steps of introducing a dilute aqueous solution of an alkali silicate selected from the group consisting of sodium and potassium silicates into an agitated aqueous receiving medium containing an alkaline earth salt selected from the group consisting of the water soluble salts of magnesium, calcium and barium or mixtures thereof; continuing the addition of said alkali silicate to said receiving medium until the pH of said receiving medium is at least 8 and for a period of time to effect an initial reaction between said alkali silicate and said alkaline earth salt; introducing a dilute solution of a salt of aluminum and a mineral acid into said receiving medium while continuing the addition of said alkali silicate; said simultaneous addition of the alkali silicate and aluminum salt being controlled such that the pH of the fluid reaction medium is in the range of 8 to 12 to thereby produce in said medium very fine white precipitated particulates composed principally of oxides of said alkaline earth metal, said alkali metal, aluminum and silicon; adjusting the pH of the fluid reaction medium to between about 8 to 10, and separating, drying and disintegrating said precipitates to obtain a pigment having a particle size of not greater than 1 micron in diameter.
 8. The method in accordance with claim 7 wherein said dilute solutions of the alkali silicate and aluminum salt are not more than 1 molar concentration and said alkali silicate contains SiO2 and Na2O in a molar ratio of from about 1 to 3.3:1, said method further comprising maintaining the concentration of said alkaline earth salt in said receiving medium such that the alkaline earth metal comprises from about 0.1 to 30.0 percent based on the dry weight of the precipitated particulate.
 9. The method in accordance with claim 7 wherein said dilute solution of the aluminum salt includes finely divided precipitated silica suspended therein. 